The overall goal of this research is to study the determinants of virulence in beta hemolytic streptococci. The techniques of recombinant DNA technology have allowed new approaches to be taken in the study of these pathogenic orgnaisms. Specifically, the multifactorial properties of the organism thought to be responsible for the disease state can now be individually isolated and subjected to intense study at the molcular level. We have isolated several genes from hemolytic streptococci which produce extracellular products known to be involved in the initiation of tissue damage; i.e., erythrogenic toxin, proteinase, streptokinase, hyaluronidase, and streptolysin O. The specific amis of this investgation are to: 1. Utilize DNA probes from the above extracellular product genes in hybridization experiments to determine the presence of these genes in a large number of streptococcal strains obtained throughout the world, and to determine whether individual determinants can be linked to strains associated with a specific disease; e.g., acute glomerulonephrintis, rheumatic fever, or scarlet fever. 2. Elucidate the study further the mechanism of toxigenic conversion by whihc lysogenic strains of S. poygenes produce the type A erythrogenic toxin. 3. Determine whether the type B erythrogenic toxin and the zymogen precursor of streptococcal proteinase are the same products, and study the determinants of these products at the molecular level. 4. Perform site directed mutagenesis and protein engineering experiments with the cloned streptokinase gene in order to study structure function relationships of this protein and also obtain second generation streptokinases. Additionally, study in further detail the group A streptokinase, which has recently been identified as te nephritis strain-associated antigen. These studies should provide information about structure function relationships of individual gene products, how they regulated, their distriubtion among streptococci and related organisms, and further insight into mechanisms of action and role in pathogenesis. Specific DNA probes will also be available for developing reapid detection and identification systems, as well as the linking of particular determinants to streptococcal strains associated with specific diseases. Finally, second generation streptokinases will be constructed which could have immediate clinical applicability in thrombolytic therapy.